--- title: "Sound Pressure Level (SPL) Sensors & Monitoring | Aethair" description: "Sound pressure level is the most fundamental acoustic measurement: the sound pressure at the microphone at a given instant, expressed on the decibel scale…" url: https://aethair.io/parameters/sound_spl/ --- Measurements · Noise # Sound Pressure Level (SPL) Also known as decibel level, dB meter, sound level Sound Pressure Level, the instantaneous weighted level (A/C/Z, fast/slow/impulse). [Schedule a call](https://calendly.com/d/ctdd-mkr-v9v/aethair-demo-website) [Configure Sound Pressure Level (SPL) Monitoring](https://aethair.io/build/?params=sound_spl) At a glance dB Noise 2 ways to measure it - **Aethair PRO** Built-in sensor - **Thiamis** 2 external instruments What it is ## What is sound pressure level (SPL)? Sound pressure level is the most fundamental acoustic measurement: the sound pressure at the microphone at a given instant, expressed on the decibel scale relative to a reference pressure of 20 micropascals, the quietest sound a healthy young ear can detect. Because the scale is logarithmic, every 10 dB rise represents a tenfold increase in acoustic energy and is heard as roughly a doubling of loudness. SPL is almost always **A-weighted** (written dB(A)) so that it tracks how the ear responds across frequency. It is reported with a **time weighting** (Fast, Slow, or Impulse) that sets how quickly the level responds to change. It is the raw quantity from which Leq and every other noise metric are derived. Because real noise fluctuates constantly, SPL is best read as a live indicator of the moment rather than a summary of exposure. **Band resolution:** reported broadband plus 1/1 octave and 1/3 octave. The metric and its frequency band are independent. Check the sound-capable devices below for what each one reports. ### Health and operational effects Loud sound damages hearing, disturbs sleep, raises stress, and masks speech and warning signals, and SPL is the number people watch to see how loud a place is right now. On a worksite or in a venue it gives immediate feedback: it shows when a machine, tool, or crowd pushes levels up so that action can be taken before exposure accumulates. It is ideal for spot checks, for confirming that a control has worked, and for triggering a real-time alarm when a threshold is crossed. What SPL does not do on its own is quantify a dose, because a single instantaneous level says nothing about how long it lasted. For that reason it is read alongside Leq, the energy-average level, which captures cumulative exposure over a period. How it is measured ## How Sound Pressure Level (SPL) Is Measured SPL is measured by a microphone and a sound level meter built to the **IEC 61672** standard, which defines Class 1 (precision) and Class 2 (general-purpose) instruments. The meter converts the fluctuating pressure into a decibel level, applies the chosen frequency weighting (usually A) and time weighting, and updates the reading many times a second. The **Aethair family includes a built-in sound sensor** that reports SPL and Leq directly, so continuous ambient noise comes from the same device that measures air quality. Where a precision or standard-compliant survey is required, an external IEC 61672 meter can instead be connected through Thiamis. Methods and guidance [IEC 61672](https://aethair.io/standards/iec_61672/) [IEC 61260](https://aethair.io/standards/iec_61260/) Built into Aethair PRO 1 Measured by the monitor's own sensors, calibrated before it ships: nothing to add. An instrument on Thiamis 2 A third-party instrument connected to a Thiamis gateway, reporting into the same Environet account. ### Placing SPL sensors For ambient indoor or area monitoring the Aethair's built-in microphone reports the level where the unit is mounted, so it is sited away from air vents, hard reflecting surfaces, and direct machine exhausts that would distort the reading. For an external microphone at a boundary or receptor, standard height and a windshield are essential, since wind across the diaphragm corrupts measurements. As with all noise measurement, the reading depends heavily on distance from the source and on nearby screening, so consistent positioning is what makes results comparable. ### Every device and option that measures Sound Pressure Level (SPL) 3 | Device / option | Type | Base platform | Measures | | - | - | - | - | | **Aethair PRO built-in sensors** | Built-in sensors | Aethair PRO | Sound Pressure Level (SPL) [Dew Point](https://aethair.io/parameters/dew_point/) [Heat Index](https://aethair.io/parameters/heat_index/) [Relative Humidity](https://aethair.io/parameters/humidity/) [Illuminance / Light](https://aethair.io/parameters/light/) [Particle Count (by size)](https://aethair.io/parameters/particle_count/) [PM1](https://aethair.io/parameters/pm1/) | | [Cirrus Research](https://aethair.io/sensors/cirrus-research-noise-monitors/) · 151B, 152B, 151A… | Noise Monitors | Thiamis | Sound Pressure Level (SPL) [Equivalent Continuous Level (Leq)](https://aethair.io/parameters/sound_leq/) [Statistical Level (Ln)](https://aethair.io/parameters/sound_ln/) [Peak Level (Lpeak)](https://aethair.io/parameters/sound_lpeak/) | | [TSI](https://aethair.io/sensors/tsi-noise-monitors/) · SP-SE-1, SP-SE-1-1/1, SP-SE-1-1/3… | Noise Monitors | Thiamis | Sound Pressure Level (SPL) [Average Level (Lavg)](https://aethair.io/parameters/sound_lavg/) [Equivalent Continuous Level (Leq)](https://aethair.io/parameters/sound_leq/) [Max Level (Lmax)](https://aethair.io/parameters/sound_lmax/) [Min Level (Lmin)](https://aethair.io/parameters/sound_lmin/) [Peak Level (Lpeak)](https://aethair.io/parameters/sound_lpeak/) [TWA / Noise Dose](https://aethair.io/parameters/sound_twa/) | [Configure Sound Pressure Level (SPL) Monitoring](https://aethair.io/build/?params=sound_spl) Where it is monitored ## Solutions That Monitor Sound Pressure Level (SPL) Each one links to the solution page showing what that industry measures it for. ### [Noise Monitoring](https://aethair.io/solutions/noise/#measure-sound_spl) Core parameter Sound pressure level is the fundamental decibel measurement underlying all noise assessment, the instantaneous level from which Leq and the other metrics are derived. Article Library ## Reading on Sound Pressure Level (SPL) ### [How to Choose an Air Quality Monitor: PRO, IAQ, or Thiamis](https://aethair.io/resources/choosing-aethair-monitoring-device/) Compare Aethair PRO, IAQ, and Thiamis to match the right device to your site, from commercial interiors to industrial and fenceline monitoring. [All articles](https://aethair.io/resources/) Related ## More in Noise [Equivalent Continuous Level (Leq)](https://aethair.io/parameters/sound_leq/) [Peak Level (Lpeak)](https://aethair.io/parameters/sound_lpeak/) [Statistical Level (Ln)](https://aethair.io/parameters/sound_ln/) [Max Level (Lmax)](https://aethair.io/parameters/sound_lmax/) [Min Level (Lmin)](https://aethair.io/parameters/sound_lmin/) [Average Level (Lavg)](https://aethair.io/parameters/sound_lavg/) [TWA / Noise Dose](https://aethair.io/parameters/sound_twa/) [Sound Exposure Level (SEL)](https://aethair.io/parameters/sound_sel/) Questions ## Sound Pressure Level (SPL) FAQ What is the difference between SPL and Leq? SPL is the instantaneous sound level at a moment in time, while Leq is the equivalent continuous level averaged over a period. SPL tells you how loud it is right now; Leq tells you the total exposure and is the metric that noise limits are written against. The two are read together: SPL for live feedback, Leq for assessment. What do Fast, Slow, and Impulse time weightings mean? They set how quickly the meter responds to changing sound. Fast reacts in a fraction of a second and follows rapid fluctuations, Slow averages over about a second for a steadier reading, and Impulse responds very quickly but decays slowly to catch short bursts. The weighting must be stated because it changes the number. Why are decibels logarithmic? Because the range of sound pressures the ear handles is enormous, a logarithmic scale compresses it into manageable numbers. A consequence is that levels do not add arithmetically: two equal sources combine to about 3 dB more, not double, and a 10 dB rise is heard as roughly twice as loud. How do I monitor sound pressure level? The Aethair family reports SPL and Leq from its built-in sound sensor for continuous ambient monitoring with alarms. For a precision or standard-compliant survey, pair a Thiamis gateway with an external IEC 61672 sound level meter instead. Use the configurator to combine sound with dust and gases in a full site configuration.